Microcontact printing can be used, for example, to generate patterns of functionalizing molecules on a surface of a substrate. The functionalizing molecules include a functional group that attaches to a substrate surface or a coated substrate surface via a chemical bond to form a patterned self-assembled monolayer (SAM). The SAM is a single layer of molecules attached by a chemical bond to a surface and that have adopted a preferred orientation with respect to that surface and even with respect to each other.
A basic method for microcontact printing SAMs involves applying an ink containing the functionalizing molecules to a relief-patterned elastomeric stamp (for example, a poly(dimethylsiloxane) (PDMS) stamp) and then contacting the inked stamp to a substrate surface, usually a metal or metal oxide surface, so that SAMs form in the regions of contact between the stamp and the substrate.
In a manufacturing process the functionalizing molecules should be reproducibly transferred from the stamp to the substrate surface in a desired high-resolution patterned SAM with a minimum number of defects. As microcontact printing speeds increase in roll-to-roll manufacturing processes on a moving web of material, pattern defects such as line blurring and voids should be minimized to ensure accurate SAM pattern resolution and reproducibility. Since the SAM patterns being generated are often very small, any relative movement between the ink laden stamp and the substrate, once contact is made, can introduce inaccuracy, distortion, or double images in the resulting printed pattern. Consistent and low contact pressure between the stamp and the substrate can reduce distortion of the small features on the surface of the stamp, and can lessen the likelihood that the thin lines on the stamp's surface are compressed or collapsed. Accurate SAM pattern transfer can allow for accurate etch patterning of the substrate, when the SAM is used as an etch mask.